Method for recovering ammonium chloride in waste liquid generated in preparation of o-nitroaniline

Abstract

The invention discloses a method for recovering ammonium chloride from waste liquid in preparation of o-nitroaniline, and belongs to the technical field of wastewater treatment. Comprising the following steps: S1, enabling the o-nitroaniline waste liquid to sequentially pass through a three-stage countercurrent washing device, and regulating the pH step by step to obtain an ammonium chloride crude extract; s2, preparing PS-DVB microspheres by taking styrene and divinylbenzene as monomers, ammonium persulfate as an initiator and polyvinylpyrrolidone as a dispersant, constructing a TiO2 shell layer on the outer layer of the PS-DVB microspheres, and then loading graphene oxide to obtain PS-DVB-coated TiO2 / GO resin; s3, the PS-DVB-coated TiO2 / GO resin is packed, the ammonium chloride crude extract is introduced into an adsorption column, effluent is collected and subjected to multiple-effect evaporation, ammonium chloride is obtained from a solid phase, and evaporated liquor and the resin are recycled and reused. Through cooperation of multiple technologies, high recovery rate, low residue and cycle economy of ammonium chloride are realized, and the method has industrial popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for recovering ammonium chloride from waste liquid in the preparation of o-nitroaniline. Background Art

[0002] o-Nitroaniline, as a basic chemical raw material, is an intermediate for many dyes, pesticides, and pharmaceuticals, and is also used in fields such as additives. The current o-Nitroaniline preparation method involves mixing o-nitrochlorobenzene and ammoniacal liquor into an ammoniation reactor, performing an ammonolysis reaction under high temperature and high pressure to produce o-Nitroaniline, ammonium chloride, and water. After separating the aqueous phase from the ammoniation product, the remaining product is washed several times with process hot water to remove the ammonium chloride, and then vacuum-dried to obtain o-Nitroaniline. Because o-Nitroaniline is slightly soluble in water, some o-Nitroaniline is dissolves and is carried away by water with each washing. Furthermore, even after several washings, the chloride ions dispersed in the o-Nitroaniline cannot be completely removed, resulting in a low o-Nitroaniline yield, poor product purity, and a high chloride ion content.

[0003] Patent application publication number CN102432033A discloses a post-treatment process for the mother liquor of high-purity o-nitro-p-chloroaniline. The mother liquor, containing ammonium chloride and a small amount of o-nitro-p-chloroaniline, is obtained by reacting 2,5-dichloronitrobenzene with ammonia to produce high-purity o-nitro-p-chloroaniline. The process uses quicklime replacement to separate the ammonia and calcium chloride from the mother liquor, which are then recycled for cost savings and green production. However, the quicklime reaction preferentially produces calcium chloride, failing to efficiently separate ammonium chloride. The high-temperature reaction (150°C) and subsequent cooling and crystallization (5-10°C) consume a significant amount of energy. Furthermore, the process fails to adsorb or extract residual nitroaniline-like organic matter in the wastewater, potentially contaminating byproducts. Patent application publication number CN107382746 A discloses a method for recovering ammonium chloride from the post-processing of o-nitroaniline. The method involves an amination reaction: nitrochlorobenzene reacts with concentrated ammonia in a six-stage series autoclave to produce an o-nitroaniline mixed solution; water washing and desalination: the mixed solution is washed with water to separate ammonium chloride, and the washing solution is adsorbed on a resin to recover residual o-nitroaniline; extraction and purification: the adsorbed liquid is extracted with o-nitrochlorobenzene to separate the aqueous phase; and evaporation and crystallization: the extracted aqueous phase undergoes triple-effect evaporation to obtain ammonium chloride, which is then recycled to recover ammonium chloride and o-nitroaniline. However, this method requires maintaining a temperature of 70–100°C and operating under reduced pressure, resulting in significant energy consumption. The resin adsorption and extraction steps increase equipment costs, and the organic solvent (o-nitrochlorobenzene) can cause secondary contamination, making the process relatively complex. Therefore, developing a method for recovering ammonium chloride from the wastewater produced by the production of o-nitroaniline is highly desirable. Summary of the Invention

[0004] The object of the present invention is to provide a method for recovering ammonium chloride from waste liquid in the preparation of o-nitroaniline, so as to improve the recovery rate of ammonium chloride from the waste liquid.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for recovering ammonium chloride from waste liquid in the preparation of o-nitroaniline comprises the following steps:

[0007] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:2-3, and the pH is adjusted step by step to obtain a crude ammonium chloride extract;

[0008] S2, using styrene and divinylbenzene as monomers, ammonium persulfate as initiator, and polyvinylpyrrolidone as dispersant to prepare PS-DVB microspheres, constructing a TiO2 shell on the outer layer of the PS-DVB microspheres, and then loading graphene oxide to obtain PS-DVB@TiO2 / GO resin;

[0009] S3. Load the PS-DVB@TiO2 / GO resin into the column, pass the crude ammonium chloride extract into the adsorption column, collect the effluent, perform multi-effect evaporation on the effluent, obtain ammonium chloride in the solid phase, and recover the evaporated liquid and resin for reuse.

[0010] Furthermore, the PS-DVB@TiO2 / GO resin is prepared by the following steps:

[0011] A1. Styrene, divinylbenzene, and polyvinylpyrrolidone were uniformly mixed to obtain a monomer mixture; ammonium persulfate was dissolved in deionized water to obtain an initiator solution; the monomer mixture and 75% ethanol solution were heated to 70-80°C under nitrogen protection, and the initiator solution was added dropwise with continuous stirring. The reaction was controlled at 70-80°C for 6-8 hours, and the reaction was centrifuged and washed, and vacuum dried to obtain PS-DVB microspheres;

[0012] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid, and ultrasonically treated at 50-60°C for 3-4 hours, washed, and vacuum-dried to obtain sulfonated PS-DVB microspheres;

[0013] A2. Dissolve tetrabutyl titanate in 75% ethanol, add a template, add acetic acid dropwise to adjust the pH to 3-4, and stir to obtain a sol; immerse the sulfonated PS-DVB microspheres in the sol, centrifuge, coat, dry, and calcine to obtain PS-DVB@TiO2;

[0014] A3. Mix the GO dispersion with PS-DVB@TiO2, perform ultrasonic treatment, centrifugal cleaning, vacuum dry, and heat treat to obtain PS-DVB@TiO2 / GO resin.

[0015] Furthermore, the weight ratio of styrene, divinylbenzene and polyvinyl pyrrolidone is (15-25): (1-3): (1-2.5).

[0016] Furthermore, the weight ratio of ammonium persulfate to deionized water in the initiator solution is (0.2-0.4): (15-30).

[0017] Furthermore, the weight ratio of the PS-DVB to concentrated sulfuric acid is 1:(8-12).

[0018] Furthermore, the weight ratio of tetrabutyl titanate to the template is (8-12): (0.8-1).

[0019] Furthermore, the template is one or a combination of F127 and CTAB.

[0020] Furthermore, the centrifugal coating condition is 3000-4000 rpm, 5-8 min, repeated 2-3 times.

[0021] Furthermore, the calcination is performed by heating the mixture to 430-450° C. at a rate of 2-5° C. / min and calcining the mixture for 2-3 hours.

[0022] Furthermore, the concentration of the GO dispersion is 0.5-1 mg / mL.

[0023] Furthermore, the heat treatment is performed at 180-200° C. for 1-2 hours.

[0024] Furthermore, the pH is adjusted step by step as follows: first stage pH = 6.0-6.5, second stage pH = 7.0-7.5, and third stage pH = 8.0-8.5.

[0025] Furthermore, the flow rate of the crude ammonium chloride extract into the adsorption column is 1-2 BV / h.

[0026] Furthermore, the evaporation temperature of the multi-effect evaporation is set to 70-100° C., and the evaporation method is reduced-pressure evaporation.

[0027] Furthermore, the stirring rate of the multiple-effect evaporation is set to 500-1000 r / min.

[0028] Furthermore, the resin recovery and reuse method is as follows: when the concentration of o-nitroaniline in the effluent reaches 0.4-0.55 ppm, adsorption is stopped, the resin is transferred to an autoclave, 150-200 mL of CO2 and 50-65 mL of ethanol mixed fluid is injected, the mixed fluid is circulated at a flow rate of 1.5-2 BV / h for 1-1.5 hours, the temperature and pressure are constant, the resin is taken out and rinsed after the pressure is reduced, and vacuum dried, and the resin can be recycled.

[0029] Beneficial effects of the present invention:

[0030] (1) The three-stage countercurrent washing device used in the present invention is combined with step-by-step pH adjustment to significantly improve the separation efficiency of ammonium chloride. The first-stage weakly acidic conditions (pH 6.0-6.5) preferentially remove free acidic impurities, the second-stage neutral conditions (pH 7.0-7.5) promote the precipitation of amphoteric metal hydroxides, and the third-stage weakly alkaline conditions (pH 8.0-8.5) reduce the residual o-nitroaniline through the electrostatic repulsion effect. This gradient washing strategy works synergistically with the countercurrent design, not only reducing the amount of washing water, but also improving the initial purity of the crude ammonium chloride extract by targeted removal of impurities in stages, which is beneficial to the subsequent adsorption and evaporation processes.

[0031] (2) The PS-DVB@TiO2 / GO resin used in the present invention not only has a high adsorption capacity, but also has regenerative properties and can be recycled. Its core layer (PS-DVB microspheres) introduces sulfonic acid groups through sulfonation treatment, which enhances the electrostatic adsorption capacity of polar pollutants (o-nitroaniline); the mesoporous structure of TiO2 in the shell layer provides a high specific surface area, while graphene oxide enhances the capture of aromatic compounds through π-π interaction. The three work together to significantly improve the adsorption capacity of o-nitroaniline; at the same time, the photocatalytic activity of TiO2 is activated during the subsequent regeneration process, and the supercritical CO2 / ethanol mixed fluid can efficiently degrade the adsorbed organic matter. The resin still maintains a high adsorption capacity after recycling. This adsorption-catalytic synergistic mechanism not only ensures a high recovery rate of high-purity ammonium chloride, but also reduces costs. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0033] Example 1

[0034] This embodiment provides a method for recovering ammonium chloride from waste liquid in the preparation of o-nitroaniline, comprising the following steps:

[0035] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.5, second stage pH = 7.5, third stage pH = 8.5) to obtain a crude ammonium chloride extract;

[0036] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0037] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0038] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min), repeat three times, dry at 60°C for 12 hours, and then calcine in a muffle furnace at 2°C / min to 450°C for 2 hours to obtain PS-DVB@TiO2.

[0039] 0.5 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0040] S3, soak the PS-DVB@TiO2 / GO resin in ultrapure water for 12 hours, rinse with ethanol three times, vacuum dry at 60°C, and load onto a column. Pass a 5% HCl solution at a flow rate of 0.5 BV / h, and then rinse with ultrapure water until neutral. Pass the crude ammonium chloride extract into the adsorption column continuously at a flow rate of 1.5 BV / h, collect the effluent, and transfer the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, perform multi-effect evaporation to obtain ammonium chloride in the solid phase, and recover the evaporated liquid for reuse;

[0041] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0042] Example 2

[0043] Compared with Example 1, this embodiment differs in that the pH concentrations at each level in S1 are adjusted. The specific implementation steps of S1 are:

[0044] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.0, second stage pH = 7.0, third stage pH = 8.0) to obtain a crude ammonium chloride extract;

[0045] The remaining raw materials and preparation process remain the same as in Example 1.

[0046] Example 3

[0047] Compared with Example 1, this embodiment differs in that the flow rate of the crude ammonium chloride extract into the adsorption column is increased, and the specific implementation steps of S3 are:

[0048] S3. Soak the PS-DVB@TiO2 / GO resin in ultrapure water for 12 hours, rinse with ethanol three times, dry under vacuum at 60°C, and then load onto a column. Pass a 5% HCl solution at a flow rate of 0.5BV / h, and then rinse with ultrapure water until neutral. Pass the crude ammonium chloride extract into the adsorption column continuously at a flow rate of 2BV / h, collect the effluent, and transfer the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, perform multi-effect evaporation to obtain ammonium chloride in the solid phase, and recover the evaporated liquid for reuse.

[0049] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0050] The remaining raw materials and preparation process remain the same as in Example 1.

[0051] Example 4

[0052] Compared with Example 1, this embodiment differs in that the flow rate of the crude ammonium chloride extract passing into the adsorption column is reduced. The specific implementation steps of S3 are:

[0053] S3, soak the PS-DVB@TiO2 / GO resin in ultrapure water for 12 hours, rinse with ethanol three times, vacuum dry at 60°C, and load onto a column. Pass a 5% HCl solution at a flow rate of 0.5BV / h, and then rinse with ultrapure water until neutral. Pass the crude ammonium chloride extract into the adsorption column continuously at a flow rate of 1BV / h, collect the effluent, and transfer the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, perform multi-effect evaporation to obtain ammonium chloride in the solid phase, and recover the evaporated liquid for reuse;

[0054] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0055] The remaining raw materials and preparation process remain the same as in Example 1.

[0056] Example 5

[0057] Compared with Example 1, this embodiment differs in that the dosage of styrene and divinylbenzene is increased. The specific implementation steps of S2 are:

[0058] S2. 24 parts of styrene (St), 2.5 parts of divinylbenzene (DVB), and 2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0059] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0060] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min), repeat three times, dry at 60°C for 12 hours, and then calcine in a muffle furnace at 2°C / min to 450°C for 2 hours to obtain PS-DVB@TiO2.

[0061] 0.5 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0062] The remaining raw materials and preparation process remain the same as in Example 1.

[0063] Example 6

[0064] Compared with Example 1, this embodiment differs in that the amount of styrene and divinylbenzene is reduced. The specific implementation steps of S2 are:

[0065] S2. 15 parts of styrene (St), 1.2 parts of divinylbenzene (DVB), and 1 part of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0066] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0067] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min), repeat three times, dry at 60°C for 12 hours, and then calcine in a muffle furnace at 2°C / min to 450°C for 2 hours to obtain PS-DVB@TiO2.

[0068] 0.5 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0069] The remaining raw materials and preparation process remain the same as in Example 1.

[0070] Example 7

[0071] Compared with Example 1, this embodiment differs in that F127 is replaced by CTAB, and the specific implementation steps of S2 are:

[0072] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0073] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0074] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 0.8 parts of CTAB, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Then, immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min) for 3 times. After drying at 60°C for 12 hours, heat the mixture in a muffle furnace at 2°C / min to 450°C and calcine for 2 hours to obtain PS-DVB@TiO2.

[0075] 0.5 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0076] The remaining raw materials and preparation process remain the same as in Example 1.

[0077] Example 8

[0078] Compared with Example 1, this embodiment differs in that the concentration of the GO dispersion is increased. The specific implementation steps of S2 are:

[0079] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0080] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0081] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min), repeat three times, dry at 60°C for 12 hours, and then calcine in a muffle furnace at 2°C / min to 450°C for 2 hours to obtain PS-DVB@TiO2.

[0082] 1 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0083] The remaining raw materials and preparation process remain the same as in Example 1.

[0084] Comparative Example 1

[0085] Compared with Example 1, this comparative example differs in that GO modification is not performed. The specific implementation steps are as follows:

[0086] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.5, second stage pH = 7.5, third stage pH = 8.5) to obtain a crude ammonium chloride extract;

[0087] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0088] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0089] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Then, immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min) for 3 times. After drying at 60°C for 12 hours, heat the mixture in a muffle furnace at 2°C / min and calcine at 450°C for 2 hours to obtain PS-DVB@TiO2 resin.

[0090] S3, soak the PS-DVB@TiO2 resin in ultrapure water for 12 hours, rinse with ethanol three times, vacuum dry at 60°C, and load onto a column. Pass a 5% HCl solution at a flow rate of 0.5BV / h, and then rinse with ultrapure water until neutral. Pass the crude ammonium chloride extract into the adsorption column continuously at a flow rate of 1.5BV / h, collect the effluent, and transfer the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, perform multi-effect evaporation to obtain ammonium chloride in the solid phase, and recover the evaporated liquid for reuse;

[0091] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0092] The remaining raw materials and preparation process remain the same as in Example 1.

[0093] Comparative Example 2

[0094] Compared with Example 1, this comparative example is different in that TiO2 coating is not performed. The specific implementation steps are as follows:

[0095] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.5, second stage pH = 7.5, third stage pH = 8.5) to obtain a crude ammonium chloride extract;

[0096] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of 75% ethanol solution were heated to 70°C under nitrogen protection, and stirred continuously (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0097] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0098] 0.5 mg / mL GO dispersion was mixed with sulfonated PS-DVB microspheres, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60°C, and heat treated at 200°C for 1 hour to obtain PS-DVB@GO resin;

[0099] S3. Soak the PS-DVB@GO resin in ultrapure water for 12 hours, rinse with ethanol three times, dry under vacuum at 60°C, and then load onto a column. Pass a 5% HCl solution at a flow rate of 0.5 BV / h, and then rinse with ultrapure water until neutral. Pass the crude ammonium chloride extract into the adsorption column continuously at a flow rate of 1.5 BV / h, collect the effluent, and transfer the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, perform multi-effect evaporation to obtain ammonium chloride in the solid phase, and recover the evaporated liquid for reuse.

[0100] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0101] The remaining raw materials and preparation process remain the same as in Example 1.

[0102] Comparative Example 3

[0103] This comparative example differs from Example 1 in that GO modification and TiO2 coating are not performed simultaneously. The specific implementation steps are as follows:

[0104] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.5, second stage pH = 7.5, third stage pH = 8.5) to obtain a crude ammonium chloride extract;

[0105] S2. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of a 75% ethanol solution were heated to 70° C. under nitrogen protection, and the mixture was continuously stirred (speed 500 rpm). The initiator solution was added dropwise, and the temperature was controlled at 80° C. to react for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and dried in vacuo at 60° C. for 12 hours to obtain PS-DVB resin;

[0106] S3, the PS-DVB resin was soaked in ultrapure water for 12 hours, rinsed with ethanol three times, and then vacuum dried at 60 ° C. and loaded into a column. A 5% HCl solution was passed at a flow rate of 0.5 BV / h, and then rinsed with ultrapure water until neutral. The crude ammonium chloride extract was continuously passed into the adsorption column at a flow rate of 1.5 BV / h, and the effluent was collected. The effluent was transferred to a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, multi-effect evaporation was performed to obtain ammonium chloride in the solid phase, and the evaporated liquid was recovered and reused;

[0107] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0108] The remaining raw materials and preparation process remain the same as in Example 1.

[0109] Comparative Example 4

[0110] Compared with Example 1, this comparative example differs in that S1 crude extraction is not performed, and the specific implementation steps are as follows:

[0111] S1. 18.5 parts of styrene (St), 1.5 parts of divinylbenzene (DVB), and 1.2 parts of polyvinylpyrrolidone (PVP) were mixed to obtain a monomer mixture; 0.3 parts of ammonium persulfate (APS) was dissolved in 20 parts of deionized water to obtain an initiator solution; the monomer mixture and 80 parts of a 75% ethanol solution were heated to 70°C under nitrogen protection, and the mixture was continuously stirred (speed 500 rpm), and the initiator solution was added dropwise. The temperature was controlled at 80°C and the reaction was carried out for 6 hours to generate a white emulsion. The microspheres were collected by centrifugation (6000 rpm, 10 min), washed with ethanol three times, and vacuum dried at 60°C for 12 hours to obtain PS-DVB microspheres;

[0112] The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid (solid-to-liquid ratio 1:10), ultrasonically treated at 60°C for 3 hours, washed with deionized water until neutral, and vacuum-dried at 60°C to obtain sulfonated PS-DVB microspheres;

[0113] Dissolve 10 parts of tetrabutyl titanate (TBOT) in 80 mL of 75% ethanol, add 1 part of F127, add acetic acid dropwise to adjust the pH to 3-4, and stir magnetically for 2 hours to form a transparent sol. Immerse sulfonated PS-DVB microspheres in the sol and centrifuge (3000 rpm, 5 min), repeat three times, dry at 60°C for 12 hours, and then calcine in a muffle furnace at 2°C / min to 450°C for 2 hours to obtain PS-DVB@TiO2.

[0114] 0.5 mg / mL GO dispersion was mixed with PS-DVB@TiO2, ultrasonicated for 1 hour, centrifuged for cleaning (3000 rpm, 3 min), vacuum dried at 60 °C, and heat treated at 200 °C for 1 hour to obtain PS-DVB@TiO2 / GO resin;

[0115] S3, soaking the PS-DVB@TiO2 / GO resin in ultrapure water for 12 hours, rinsing it with ethanol three times, vacuum drying it at 60°C, and loading it into a column. Passing 5% HCl solution at a flow rate of 0.5BV / h, and then rinsing it with ultrapure water until it is neutral, continuously passing the o-nitroaniline waste liquid into the adsorption column at a flow rate of 1.5BV / h, collecting the effluent, and transferring the effluent into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, multi-effect evaporation is performed to obtain ammonium chloride in the solid phase, and the evaporated liquid is recovered and reused;

[0116] When the concentration of o-nitroaniline in the effluent reaches 0.5 ppm, the adsorption is stopped, the resin is transferred to an autoclave, and a mixed fluid of CO2 and ethanol (CO2 150 mL, ethanol 50 mL) is injected. The mixed fluid is circulated at a flow rate of 2 BV / h for 60 minutes, and the temperature and pressure are kept constant. After the pressure is reduced, the resin is taken out, rinsed with ultrapure water 3 times, and vacuum dried at 60°C for 12 hours. The resin can then be recycled.

[0117] The remaining raw materials and preparation process remain the same as in Example 1.

[0118] Comparative Example 5

[0119] Compared with Example 1, this comparative example differs in that S2 resin adsorption is not performed, and the specific implementation steps are as follows:

[0120] S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:3, and the pH is adjusted step by step (first stage pH = 6.5, second stage pH = 7.5, third stage pH = 8.5) to obtain a crude ammonium chloride extract;

[0121] S2. The crude ammonium chloride extract is transferred into a multi-effect evaporator. After setting the evaporation temperature in the evaporator and the stirring rate of the stirrer on the evaporator, multi-effect evaporation is performed to obtain ammonium chloride in the solid phase.

[0122] The remaining raw materials and preparation process remain the same as in Example 1.

[0123] Performance Testing

[0124] Examples 1 to 8 and Comparative Examples 1 to 5 were tested for ammonium chloride recovery (%), ammonium chloride purity (%), residual o-nitroaniline (%), and regeneration efficiency after 50 cycles (%);

[0125] The results are shown in Table 1:

[0126] Table 1

[0127]

[0128]

[0129] As can be seen from Table 1, by comparing the data of Examples 1-4 and Comparative Example 4, it can be seen that the three-stage countercurrent washing combined with pH gradient control has significant advantages:

[0130] The recovery rate (98.5%) and purity (99.2%) of ammonium chloride in Example 1 (pH 6.5 → 7.5 → 8.5) were significantly higher than those in Comparative Example 4 (unwashed, recovery rate 88.4% and purity 96.5%), indicating that gradient pH washing effectively removed impurities and improved the initial purity of the crude extract. The data from Example 2 (adjusting the pH range) and Examples 3-4 (changing the flow rate) show that precise control of the pH gradient design plays a key role in impurity removal. Weakly alkaline conditions (pH 8.5) reduce o-nitroaniline residues through electrostatic repulsion (0.003% residue in Example 1 vs. 0.061% in Comparative Example 4).

[0131] Example 1 (0.003% residual o-nitroaniline) is significantly better than Comparative Example 1 (no GO modification, 0.031% residual) and Comparative Example 2 (0.054% residual). This is due to the synergistic effect of the shell: the mesoporous structure of TiO2 provides a high specific surface area, and GO enhances adsorption through π-π interaction. The synergistic adsorption capacity of the two reaches 450 mg / g (traditional resin is only 120 mg / g). The regeneration efficiency of Example 1 after 50 cycles is 92.7%, which is much higher than Comparative Example 3 (62.5%). The supercritical CO2-ethanol mixed fluid efficiently desorbs organic matter through synergistic dissolution and TiO2 photocatalytic degradation. The performance of Example 7 (CTAB template) is slightly lower than that of Example 1 (F127 template). This is because the pore size formed by CTAB is smaller, which limits the uniformity of GO loading, resulting in a slightly higher residual amount.

[0132] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A method for recovering ammonium chloride from waste liquid in the preparation of o-nitroaniline, characterized in that: The following steps are involved: S1, the o-nitroaniline waste liquid is sequentially passed through a three-stage countercurrent washing device, with the volume ratio of washing water to waste liquid in each stage being 1:2-3, and the pH is adjusted step by step to obtain a crude ammonium chloride extract; S2, using styrene and divinylbenzene as monomers, ammonium persulfate as initiator, and polyvinylpyrrolidone as dispersant to prepare PS-DVB microspheres, constructing a TiO2 shell on the outer layer of the PS-DVB microspheres, and then loading graphene oxide to obtain PS-DVB@TiO2 / GO resin; S3. Load the PS-DVB@TiO2 / GO resin into the column, pass the crude ammonium chloride extract into the adsorption column, collect the effluent, perform multi-effect evaporation on the effluent, obtain ammonium chloride in the solid phase, and recover the evaporated liquid and resin for reuse.

2. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 1, characterized in that: The PS-DVB@TiO2 / GO resin is prepared by the following steps: A1. Styrene, divinylbenzene, and polyvinylpyrrolidone were uniformly mixed to obtain a monomer mixture; ammonium persulfate was dissolved in deionized water to obtain an initiator solution; the monomer mixture and 75% ethanol solution were heated to 70-80°C under nitrogen protection, and the initiator solution was added dropwise with continuous stirring. The reaction was controlled at 70-80°C for 6-8 hours, and the reaction was centrifuged and washed, and vacuum dried to obtain PS-DVB microspheres; The dried PS-DVB microspheres were immersed in 98% concentrated sulfuric acid, and ultrasonically treated at 50-60°C for 3-4 hours, washed, and vacuum-dried to obtain sulfonated PS-DVB microspheres; A2. Dissolve tetrabutyl titanate in 75% ethanol, add a template, add acetic acid dropwise to adjust the pH to 3-4, and stir to obtain a sol; immerse the sulfonated PS-DVB microspheres in the sol, centrifuge, coat, dry, and calcine to obtain PS-DVB@TiO2; A3. Mix the GO dispersion with PS-DVB@TiO2, perform ultrasonic treatment, centrifugal cleaning, vacuum dry, and heat treat to obtain PS-DVB@TiO2 / GO resin.

3. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 2, characterized in that: The weight ratio of styrene, divinylbenzene and polyvinyl pyrrolidone is (15-25): (1-3): (1-2.5); the weight ratio of ammonium persulfate and deionized water in the initiator solution is (0.2-0.4): (15-30).

4. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 2, characterized in that: The weight ratio of the PS-DVB to concentrated sulfuric acid is 1:(8-12).

5. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 2, characterized in that: The weight ratio of tetrabutyl titanate to the template is (8-12): (0.8-1); the template is one or a combination of F127 and CTAB.

6. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 2, characterized in that: The centrifugal coating conditions are 3000-4000 rpm, 5-8 minutes, repeated 2-3 times; the calcination is to increase the temperature to 430-450° C. at 2-5° C. / min and calcine for 2-3 hours.

7. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 2, characterized in that: The concentration of the GO dispersion is 0.5-1 mg / mL; and the heat treatment is performed at 180-200° C. for 1-2 hours.

8. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 1, characterized in that: The pH is adjusted step by step as follows: the first stage pH = 6.0-6.5, the second stage pH = 7.0-7.5, and the third stage pH = 8.0-8.

5.

9. A method for recovering ammonium chloride from waste liquid for preparing o-nitroaniline according to claim 1, characterized in that: The flow rate of the crude ammonium chloride extract into the adsorption column is 1-2 BV / h; the evaporation temperature of the multi-effect evaporation is set to 70-100° C., the evaporation method is reduced pressure evaporation; and the stirring rate of the multi-effect evaporation is set to 500-1000 r / min.

10. The method for recovering ammonium chloride from waste liquid produced during the preparation of o-nitroaniline according to claim 1, wherein: The resin recovery and reuse method is as follows: when the concentration of o-nitroaniline in the effluent reaches 0.4-0.55 ppm, adsorption is stopped, the resin is transferred to an autoclave, 150-200 mL of a mixed fluid of CO2 and 50-65 mL of ethanol is injected, the mixed fluid is circulated at a flow rate of 1.5-2 BV / h for 1-1.5 hours, the temperature and pressure are kept constant, the resin is removed after the pressure is reduced, rinsed, and vacuum dried, and the resin can be recycled.

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